pnacl driver: add support of Objective-C source files.
pnacl driver: add support of Objective-C source files.

This was requested by a group of students at Carnegie Mellon University which are trying to compile Objective-C programs to PNaCl.
Review URL: http://codereview.chromium.org/8166002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@6850 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client